The field of the invention is that of analyzing vibration, and more particularly vibration in an appliance that is provided with an engine driving a rotary propulsion member. A typical example of an application of the invention is a helicopter, a vehicle which presents a high level of vibration that is due essentially to the main rotor serving to support the helicopter and to enable it to move.
It is important to characterize the vibration present in such a vehicle since vibration is a sign of stresses that can lead to a fatigue phenomenon and that therefore have a direct influence on safety. Vibration can also degrade the performance of various items of equipment installed on the vehicle. In addition, vibration in a helicopter cabin is instrumental in determining passenger and pilot comfort. It goes without saying that pilot comfort is also an essential feature for safety.
Thus, a system is known for continuously recording vibration within a helicopter, which system is known as a health usage monitoring system (HUMS). The system records a warning in a removable monitoring cartridge if the level of vibration exceeds a predetermined threshold at a frequency Ω, 2Ω, or BΩ, where Ω represents the speed of rotation of the rotor and B the number of blades mounted on the rotor. The warning can be detected only in a ground station equipped to play back the information recorded in the cartridge. The pilot does not have access to this information while on a mission. In addition, no means is provided to give an overall assessment of the vibration level that is not restricted to an identified frequency, but rather reflects the overall behavior of the vehicle.